The present invention relates to methods and devices for use in the monitoring of the ovulation cycle in female mammals, especially humans.
Many monitoring methods have been proposed, based on a wide variety of physical or chemical bodily changes believed to be indicative of the progress of the ovulation cycle. Examples are to be found in:
U.S. Pat. No. 3,749,089 which describes an instrument for monitoring ovulation including a dual electrode vaginal probe and monitoring device, for indicating the magnitude and polarity of the electriochemical response of vaginal fluids.
U.S. Pat. No. 3,924,609 which describes a test procedure and apparatus for determining low DC potentials for measurement and identification of the different phases as well as the fact of ovulation in adult mammalian females.
U.S. Pat. No. 3,926,037, U.S. Pat. No. 3,928,423, U.S. Pat. No. 4,002,056, U.S. Pat. No. 4,013,066 and U.S. Pat. No. 4,059,986, which describe devices for determining the properties (particularly surface tension) of bodily mucus as an indication of menstrual cycle phase.
U.S. Pat. No. 3,986,494 and U.S. Pat. No. 4,010,738, which describe a method of monitoring the concentration of volatile organic compounds having a molecular weight of between 50 and 350, found in vaginal secretions.
U.S. Pat. No. 4,031,365 describes a system for continuously monitoring and displaying temperature to indicate ovulation activity.
U.S. Pat. No. 4,036,212 describes a method of monitoring the progress of the ovulation cycle which comprises periodically determining the concentration of ATP in vaginal fluid.
U.S. Pat. No. 4,119,089 describes a method for predicting and ascertaining the time of ovulation by monitoring the level of at least one volatile sulphur compound commonly occurring in mouth air.
U.S. Pat. No. 4,148,304 describes a system for determining the time of ovulation in females including a probe which measures body temperature and a probe which measures body potential together with an electronic amplification circuit and indicating device which is capable of measuring small changes in temperature and body potential and providing a portable and convenient device for determining time of ovulation.
U.S. Pat. No. 4,151,831 describes a fertility indicator for measuring and detecting the body temperature of a human subject over a menstrual cycle, having a timer for generating time based signals, and a logic circuit connected to the clock timer and being responsible to the time based signals for selecting the proper combinations of the time based signals and for indicating the correct present time. There is a temperature sensor coupled to the logic circuit for measuring the body temperature of the human subject. A solid state memory circuit having coded information command signals is coupled to the logic circuit for sequencing the logic circuit to take a plurality of temperature readings at a preset real time and to terminate the readings when the temperature has stabilized. A data storage circuit is provided for sequentially recording each of the stabilized temperatures that were measured, and a display circuit responsive to the solid state memory and data storage circuits, indicates the status of fertility of the subject during a menstrual cycle. There is also an alarm circuit coupled to the logic circuit and it has a variable pitch responsive to the solid state memory circuit for indicating the time when the subject's temperature has to be taken. Lights or words can indicate the user's status.
U.S. Pat. No. 4,151,833 describes a method for detecting ovulation by measuring the water content of the cervical mucus using a pellet made from a water-swellable polymer.
DE 2803152 describes a pregnancy preventing system using an instrument incorporating a tape cassette for recording data, a micro processor, a digital clock, an electrical temperature recorder, an acoustic signalling device, and indicator lamps.
EP 11594 describes a "pocket calculator" for forecasting menstrual cycle, using regularly entered data to predict the probability of conception.
DE 2847397 describes a microprocessor family planning calculator programmed to evaluate safe period of birth control and designed to be coupled to an existing electronic device, such as a digital alarm clock. The device includes input keys to allow data and time to be entered and an additional key to be operated at the commencement of menstruation.
U.S. Pat. No. 4,246,907 describes a method for predicting ovulation based on measuring every day throughout at least a substantial portion of the days of the menstrual cycle, the polarity of a direct current potential between at least two spaced apart portions of a woman's body.
U.S. Pat. No. 4,465,077 describes a fertility computer having the ability to store information about a user's past menstrual cycle history, basal body temperature, and gynaecological disorders which, along with certain prediction indicators, is used to predict statistically when ovulation will occur. The information is processed in accordance with a pre-determined program which ascribes certain values to the parameters to predict the present fertility status of the user.
There is at least one ovulation prediction device available commercially at present for home use which relies on the measurement of basal body temperature (BBT) and incorporates a micro-processor which adapts its prediction of the current cycle in accordance with measurements taken during preceding cycles.
Of the various methods set forth above, those utilizing the regular measurement of BBT are probably the most logical and accurate. Nevertheless, the use of BBT measurement alone is insufficiently reliable to provide an indication of the cycle status which is sufficiently accurate for contraceptive purposes. The proposal in U.S. Pat. No. 4,465,077, which combines temperature measurement with other indicators, may represent an improvement, but the additional indicator used (vaginal mucus change) is not a parameter that we believe is sufficiently significant or reliable.
Furthermore, a drawback of methods which rely primarily on the change in BBT to estimate the time of ovulation is that they are only really good at predicting the second infertile phase of a cycle occurring after ovulation (luteal phase), since the rise in BBT that occurs after ovulation can only be used to identify ovulation after it has occurred. In the absence of another reliable indicator, the first infertile phase of a cycle can only be estimated using a calendar, and a knowledge of BBT and other factors from previous cycles. In this event, it must be falsely assumed that ovulation does not occur either earlier or later than estimated. Should ovulation occur earlier than estimated, the fertile part of the cycle will commence earlier than estimated. Should ovulation occur later than estimated, then the rise in BBT that occurs after ovulation and can be used to predict the luteal phase will not occur until later than estimated; therefore, the fertile part of the cycle will have been erroneous estimated as having started earlier than it actually did, and therefore is estimated as being unduly long.